Add default term size and toggle feature enhancement

[xavier-balesi]

Hi ! I like your plugin and I have add some little features.

• if term is shown but the focus is on another window, :ToggleTerminal will just focus on the term window (and not hide it)
• default size (= 20)

Do you think I can make a PR ? Thank you :)

[pakutoma]

Hi! The features are great!

The first feature changes the behavior of this plugin. Such a feature should be able to be turned off in the configuration file.

Pull request is very welcome😀 I'm sure it will be merged soon.

[xavier-balesi]

Hi! Cool, I have add the focus feature optional. Should I fork the repo to make the PR or you could add me as contributor ?

Thank you :)

[pakutoma]

Please fork and make the PR. Thank you.